Submarine sound receiver



W. HAHNEMANN SUBMARINE SOUND RECEIVER Filed Sept. 30, 1920 Patented May 22, 192`8.

UNITED STATES l Lamas PATENT ortica.

WALTER FIRM SIGNAL GESELLSCHAFT M. H., OIF KIEL, GERMANY.

SUBMARINE SOUND' RECEIVER.

Application filed September 30, 1920, Serial This invention relates to submarine sound receiving devices which consist of a tuned body or structure that collects or takes in the sound waves and a sound detecting de- 6 vice coupled to the said body or structure.

The perception underlying the invention is that in a receiving device of this kind not only the natural rate of vibration of the sound collecting structure thaty takes in the lo sound waves, but also the natural rate of vibration of the detecting device, should not be arbitrary. The detecting device should be tuned to a certain natural tone, and

should act in accordance with this tuningi 16 when used. If two previously tuned vibratory structures of the said kind are coupled to each other a resonance curve will be obtained with two diierent maxima or crests the positions of which are determinedby the 20 natural periodic time of the individual vibratory structures and the nature of the coupling between them.

' But z-in submarine sound receivers of the said kind the evil has' hitherto existed that the acoustic properties of the receiver changed when the detecting devices in the apparatus were exchanged; because it was not taken intoconsideration that these detectors themselves acted as vibratory struc tures and as such possessed certain characteristics of their own, and because the tuning of the individual partsin different detecting devices of one and the same type was not at all uniform. Besides, in subma-A rine sound signalling devices in which detectors are used that possess imperfect pressure contacts, the acoustic properties of the parts of thedevice change whilev the devices are in use, where no measures are adopted to `keep their individual tunings permanently constant. These facts are particularly anj noying when the parts oi the detectorare used in conjunction with acoustic structures such as tuning forks that are tuned to a certain tone. It, for example, a detector of this kind is mounted between the two prongs of a. tuning fork-when the changes of pressure' against the detector due to the prongs vibrating in opposite. directions will be utilized for the function of the receiving-a combined resonance will occur inthe receivingsystem which, of course, will be partially Y determined by the nature of the vlbrations of the detector structure and will therefore change as the nature of these vlbrations No. 413,944, and in Germany October 7, 1914.

changes. It is thus seen'that herealso the changes in the individual tuning'of the de-y tector have to be taken into cons1deration.

The object of this invention is to remove the afore-mentioned drawbacks of the known structures employed in receiving devlces, and this is accomplished by a certain combination of certain measures in produclng the receivers. lIt consists more particularly in tuning both the body or structure HAHNELLANN, or xr'rznnnne, NEAR KIEL, GERMANY, AssIeNon. 'ro man I that takes in the sound waves (diaphragm),

and the detector, of each `device in such a manner as to cause each to execute certain predetermined natural rates of vibration, which, when the two tuned structures are coupled together to a certain degree, will give a receiving system or-device having two frequencies of resonance, one of which will coincide with the tone used for signalling. Hence in accordance with the invention the treatment to which the' detector is subjected during its production is such that the predetermined natural rate of vibration will be the immediate result of the elasticity and dimensions of its parts and of its design, so

detectors, if made of the same material and having the same dimensions, will always recur. These premises,'an`d a due consideration of the degree of the acoustic coupling between the detector and the tuned sound collecting member when effecting the tun# ing, are necessary if the position of the crest in the resonance curve is to remain unchanged when the detector of the receiving device is replaced. In order to obtain the necessary permanency of the4 tuning in microphones during their operation, certain special measures which constitute features of this invention must of course be carried out in producing the same. In accordance with the invention the flanges that grip the edge of the microphone diaphragm areA inglsurface of the diaphragm is always kept perfectly constant. In microphonic detectors in which an electrode bears against the casing of the device, the bearing surface of this electrode is also made hollow so that a sharp Jor well define/dI edge of the same is pressed against the casing in order to obtain a close and uniform Contact.

A constructional form of la submarine sound receiver constructed in accordance with the above-described methodf is shown ment that establishes an electrical connec-v tion between the two electrodes f and b.

The lateral boundaryof the granule chamber is formed of a soft ring d which is formed of felt or silk and bears against the casing e. The second electrode is formed in the shape of a disk f which is fixed at the niiddle of the diaphragm by means of a nut g. The threaded stem s that .carries the nut g also serves'to connect the microphone with the tuned diaphragm m that collects or takes lin the sound waves. To this end the threadedstem s is made to pass through the 'is screwed fast. The supportin diaphragm m and is held in position by a nut n. u is a metal seal on the outside of the diaphragm and r a' washer l011 the' inside of the diaphragm. Connected externally to the electrodes of thefmicrophone are the wires i that carry the currentwhose strength is altered by the changes of resistance produced by alterations of the pressure exerted on the anules with' which the chamber c is lille The surface of the electrode f that bears against the supporting plate a is hollow or concave, as indicated in the drawing, so that .it pressed into -iirm contact with the diaphragm when the nut g plate a is made in the shape of a tuned aphragm and preferably consists of a metal such as brenne. At its edge the diaphragm is fixed to the fiange of the casing by means of a ring In manufacturing the detector the ring and the liange are ground upon each other,

as hereinbefore mentioned, to provide even 'surfaces thereon sothat the diaphra may 'be gripped vfirmly and uniformly tween the ring and fiange and the inner edge of the ring and fiange mayV lie close against the diaphragm. This latter feature 1s of impartance, since if the inner edges-of the ring did not lie close against the diaphragm t e radial distance'R, representing the width of the freely vibrating or unrestrained portion of the diaphragm, would be increased' and thus the tuning of the preferabl tuning before hand the ymicro'phonic detector to a natural rate of Vibration so high that the frequency of resonance of the coupled system resulting after coupling the detecting device with the wave collecting member and corresponding tothe natural rate of vibral tion .of the dbtecting device is greater than the tone used for signalling. In receiving devices comprising a soundwave collecting diaphragm and a microphonic detector, the natural rate of vibration of the diaphragm will be chosenso that the frequency o resonance of the receiving device which corresponds tothe rate of vibration of the diaphragm coincides with the tone used for si sary that t e frequency of the natural rate of vibration of the diaphragm be higher than the fre' uency af the tone used for signalling. A vantageously the frequency of the natural rate of vibration of the microphonie detector then will be chosen so as to be higher than the frequency of the diaphragm by approximately'the same amount as the latter is higher thanthe tone used for signalling.

I claim: v u

1. In a submarine sound receiver, a sound collectind member, andl a detector, said sound cdlleetin member and said detector alling. In this case it is neceseach being in 'vidually tuned and means for couplin them together acoustieally the dominant equeneies ofresonance of the cou led system embracing the frequency use for signaling'. Y

2. In a submarine sound receiver, a sound collecting member, and a detector, said 4. Ina submarine soun receiver, a sound sound eollectin i member and said detector v e R d 3 *I provided with a. suppo ing e'; an elas tic diaphragm supported oii slriange; a ring for holding the edge of the diaphragm securely against said supportingange; said ring andfsaid supporting flange ve'ing ground 70 oi upon'each other so asto provide smooth and uniform contactwithrv the diaphragm; anelectrode secured to said casing; an oppositel7 disposed electrode .secured to/thel central part of Ythe diaphragm, said 'electrode 75 comprisingl a plate having a concave surface. in engagement with'the diaphragm,a screw pin connected with theY plate and passing through the diaphralrmand a nut to be screwed on the pin to aw the plate securely 80' against the fdiaphragm; and carbon granules -in the casing establishing connection nbeJ tween the two electrodes.

`collecting member anda detector, said sound collecting member' and said detector. each beingA individually. tuned and means k for acoustically couplin them together one [of Hthe two dominant equencies of resonance oftheeou led system, namely the i'e uencyg oor n to the detector, being igher -than e frequency 4used for signaling. p

5. In a-subniarine.soundieceivei,a` sound lo collecting member and a detector, said sound d /collectingniember and said detector each Lbeking individually tuned and means for acousally coupling themtogether one ofthe Y two dominant frequenies of, resonance of l5 the coupled system, namely the frequency corresponding to the' -sound collecting memb er, coinciding with the frequency used for 6. In a submarinesound receiver, asound.

llecting diaphragm, and a microphonic de. tor, said diaphragm being individuallyv tuned to a :frequency higher than that used for signaling,said detector being individui ally timed to a frequency higher than that of the diaphragm 'by about the same amount that the frequencyl of the diaphragm is higher than the sign "frequency,`and the tuned diaphragm an etector 4being -acoustically coidipled together in such relation that onesof the twordoinina'nt frequencies i of resonance of the coupld system, namely the frequency .corresplondingmto .the diaphragm, coincides wtht e trequencyused for signaling.

J 7. In a tuned sounddetecting microphone, a cup-like casing provided with an annular v 11. A1 'microphone comprising a provided with a supporting ange; an elas-'. 85 tic diaphragm supported on saidsange; a ring for holding t eedge of ,the diaphragm securely against said supportingilange; said ring .and said supporting flange eing ground od upon each other so as-to provide smooth 90 and uniform contact with the. diaphragm; an electrode secured to said casing; an oppo# sitely disposed electrode secured to the central part of the diaphragm, said electrode 'comprising a pl e havin a concave surface -95 in engageme'iit with the 'aphragm, a screw pin connected 'with said plate and passing 'through the diaphra and. a nut to be screwed on the pin to aw the plate securely against the diaphragm; saidk nut having -aperipheral -iiange,Y a vbratory diaphragm seatedon said flange, and an annular clamping member for clamping' the peripheral pordiameter substantially 'equal to that of the plate' and'beng provided with a concave-surface inengagement with the plate; and car# f tion of said diaphragm securely on said M ange, the diaplira -engaging surfaces of the il and of e clampn memberbeinggro nd oi on each other -efore clamp-f ing the diaphragm therebetween so -thata e uniformand secure claipf eect issecured whereby the areaof e eely vibratable Aportion of the' diaphragm remains constant. 8,."In atuned sound etecting microphone, a vibratory diaphragm, and an electrode lying against and secured to thevcentral por- 511 'tioirof'said' da h ragm, saidelectrode hav 'jmg its diaphran-enga surface in concave -frm andbeing-provi ed with-a screwthreaded pin which-passes through the dia-- phragm, and? a niit havingfa 'concave f dia- 5?" @kraam-ausgang; surface adapted te as f screwed-v tj saidpin and against said da# phragm' rmlyclamp the diaphragm between the lelectrode and the nut in such 2 v'mannen that theclamped area of the diaphragm does not vary during' vibration of Athe diap ragni. L

'p 9. A evice acgording to claim '8 in'which l ,the boundaries of the clamping surfaces ofV signature. v.the velectrode and the' nut are in alinement. 10.v Av micrpphone comprising a. casing bon granules in the casing establishing connectin between/'the two electrodes.

12. A microphone comprising a casing provlilded with a suppirting flnge; an elastic diapragm. porte on sai nge; aring for holdingste edge othe diaihragm securely against said supporting anga, said ring and said supporting Bange being ground od upon each other so as to provide smooth -and uniform contact .with theA diaphragm; an electrode secured to thecentraLpart of `the diaphragm, said electrode comprising a plate havin a eonqa e surface in engagement with e diaph gm,l a screw pin connected with theplate andpassing through the diaphragm, and a nut tol be screwed on Vthe pin to 'draw the plate securely against the diaphragm; an oppositely disposed second 'electrode having a concave surface inf contact with the casing; means for pressing said second lectrode-close against thec'a'sing; 1 and carbon granules in the casing establishmonnection between the'two electrodes. f testimony whereof I have axed my iis WALTER i .A 

